In process control for industrial plants, there are sensors for sensing physical measurements for the process being run (e.g., pressure, temperature, level, or fluid flow) and instruments for performing monitoring and/or control output actions (e.g., control valves, actuators, drive units or tank sensors) for the processing units in the plant. These instruments are generally referred to as “field devices” or “field instruments” (hereafter “field devices”), which may be located in areas that are either manned or unmanned. These field devices are associated with the processing equipment (e.g. tanks, pipelines, boilers) which is part of the process control. For example, the tank gauging systems typically involve tank sensors measuring the product inventory relevant properties within the tanks. Tank gauging systems are widely used in application areas involving handling, shipping and storing of products, as well as in the chemical process industry.
In an industrial process control system, a communications device including a transceiver is used for scanning the field devices at a regular interval of time to generate measurement data such as product level, temperature, pressure, density data, and a communicably connected host computer performs process monitoring and/or for process control. The communications device comprises a processor with Inputs/Outputs (I/Os) functioning as a bridge (an IO device). A typical local polling system uses a clock to provide a control signal to the CPU of the communications device at predetermined intervals. Upon receiving the clock signal, the CPU initiates a signal for the communications device to begin polling each field device at a predetermined regular (constant) interval of time.